1. Field of the Invention
The present invention relates to a composition comprising a polyolefin resin and an engineering resin. Particularly, the present invention relates to a resin composition comprising (A) a modified polyolefin resin obtained by introducing a group selected from a) hydroxyl group, b) epoxy group and c) carboxyl group into a crystalline olefin copolymer consisting of at least one of ethylene and .alpha.-olefins each having 3 to 8 carbon atoms and at least one chain non-conjugated diene, and (B) a polyamide resin or saturated polyester resin. The resin composition has good basic characteristics such as impact resistance, rigidity, heat resistance, moldability, moisture resistance and chemical resistance, all of which are required for molding materials for automobile parts, electric product parts and the like.
2. Description of the Related Art
Polyolefin resins are widely used as molding materials because they are inexpensive and have excellent mechanical strength, moldability, moisture resistance and the like. In order to widen the application field of polyolefin resins, an attempt is made to mix the polyolefin resins with engineering plastics such as polyamide resins or the like so as to improve heat resistance and rigidity.
Since polyamide or saturated polyesters generally have poor compatibility with polyolefins, a finely uniform mixing state cannot be obtained by simply mixing using an extruder or a molding machine, so obtained article has a poor impact strength. In order to improve the compatibility, a method has been proposed in which a functional group such as a carboxyl group, an epoxy group or the like, which is expected to produce bonding reaction with a polyamide or saturated polyester, is introduced into a polyolefin having poor reactivity to form a modified polyolefin which is then mixed with a polyamide or saturated polyester (for example, Japanese Patent Publication No. 45-30945). Another method is described in "Polymer Chemistry" Vol. 29, 265 pp (1972) in which crystalline polypropylene and polyamide are mixed in the presence of maleic anhydride-modified polypropylene. Japanese Patent Publication No. 57-59216 and Japanese Patent Laid-Open No. 58-105448 disclose compositions each comprising a saturated polyester resin and a maleic acid-modified polyolefin.
Although the technique of improving impact resistance strength by mixing a polyamide resin with an ethylene-glycidyl methacrylate copolymer is generally known, copolymerizable olefin species are limited, and sufficient properties with respect to rigidity and heat resistance are not obtained in the present situation. Japanese Patent Laid-Open No. 51-144452 discloses that polyalkylene terephthalate is mixed with a polyolefin modified with a glycidyl ester of an .alpha.,.beta.-unsaturated carboxylic acid for the purpose of improving impact resistance strength.
The method of producing modified polypropylene by grafting polypropylene with maleic anhydride or glycidyl acrylate under conditions of radical reaction is widely known (Japanese Patent Laid-Open Nos. 59-62613 and 61-266411). However, the radical grafting method generally has a low grafting rate and grafting efficiency. If an attempt is made to increase the modification degree, the method causes the problem that undesirable reaction such as molecular breakage, crosslinking or the like of the main polymer to be grafted easily takes place, and thus a highly modified product cannot be obtained. These methods realize the production of compositions each comprising a modified polyolefin and a polyamide or polyester in a finely dispersed state and achieve the purpose of improving the balance of properties such as impact resistance strength, heat rigidity and the like. However, nowadays, there is a demand for further improving the properties.
It is an object of the present invention to provide a composition comprising a polyolefin resin and a polyamide resin or a saturated polyester resin and having improved impact resistance strength. Particularly, it is an object of the present invention to find a novel modified polyolefin having further improved compatibility with polyamides or saturated polyesters and obtain a composition having good compatibility which cannot be attained by the prior art.